Generally, the computerized numerically controlled lathe automatically processes a work piece by using a computer on a basis of a pre-programmed process condition such as a target processing measurement, a desired shape, a transferring speed of the cutting tool, etc. Since this lathe is profitable to the factory automation and the mass production, it has been widely used in various applications.
FIG. 1 shows the conventional computerized numerically controlled lathe 10.
Referring to FIG. 1, the computerized numerically controlled lathe 10 comprises a frame 12 including a bed 12a, a headstock 14 for grasping and fixing one end of the work piece, which is fixed at one side of the frame 12, a tailstock 16 for grasping and fixing the other end of the work piece, which is sliderably positioned on the bed 12a in opposite to the headstock 14, a tool rest 18 for processing the work piece rotated between the headstock 14 and the tailstock 16 while moving along the longitudinal axis of the bed 12a on one side portion of the bed 12a of the frame 12, a control part (not shown) for controlling the headstock 14, the tailstock 16 and the tool rest 18.
The work piece, which is supported and rotated between the headstock 14 and the tailstock 16, is automatically processed by the cutting tool mounted to the tool rest 18 sliding on the bed 12a on a basis of the pre-programmed process condition.
However, problems with the conventional computerized numerically controlled lathe as described above are that a cutting edge of the cutting tool for processing the work piece may be worn due to the friction between the cutting edge and the work piece and the processing precision of the cutting tool may deteriorate due to the change of the cutting tool's position. Another problem which is inherent to such known computerized numerically controlled lathe is that, when the old cutting tool has been changed with a new cutting tool, it is extremely difficult to obtain an accurate treatment of the work piece due to the difference of positions between the old cutting tool and the new cutting tool.
A variety of endeavors for solving these problems have been proposed. One approach, a program for compensating the cutting tool's position so as to compensate a positional deviation between the coordinates of the cutting tool for processing the work piece and the standard coordinates in order to enhance the processing accuracy of the cutting tool during operation of processing the work piece, has been proposed.
This program is preprogramedly input into the computerized numerically controlled lathe 10.
FIG. 2 shows the apparatus for detecting a position of the cutting tool mounted to the computerized numerically controlled lathe, more particularly shows the apparatus for detecting the position of the cutting tool mounted to the headstock of the computerized numerically controlled lathe.
As shown in FIG. 2, the apparatus 20 for detecting the position of the cutting tool comprises an arm 22 having a touch sensor 22a for sensing the position of the cutting tool, a gear assembly 24 for pivoting the arm 22 toward the cutting tool, and a driving motor (not shown) for driving the gear assembly 24.
At the apparatus 20 for detecting the position of the cutting tool, the arm 22 having the touch sensor 22a is moved toward the cutting tool by means of the gear assembly 24 and then the cutting tool is brought into contact with the touch sensor 22a in accordance with the program that is preprogramedly input into the computerized numerically controlled lathe 10. At this time, the touch sensor 22a provides the control part of the computerized numerically controlled lathe with a sensing signal.
As soon as the sensing signal is input into the control part from the apparatus 20 for detecting the position of the cutting tool, the control part of the computerized numerically controlled lathe recognizes the position of the cutting tool. Then, the control part compares the detected value relative to the position of the cutting tool with a standard value and then calculates a displacement of the cutting tool. Finally, the control part provides the tool rest with the control signal for compensating the position of the cutting tool based on the displacement of the cutting tool calculated.
Accordingly, it is possible to compensate the position of the cutting tool such that the front end's position of the cutting tool corresponds to the initial state of the cutting tool, which is preprogramedly set into the computer.
However, one problem with the apparatus for detecting the position of the cutting tool as described above is that the arm having the touch sensor must be maintained at a sensing position until the cutting tool is brought into contact with the touch sensor after moving the touch sensor to the sensing position so as to minutely compensate the position of the cutting tool. Accordingly, the driving motor must be continuously operated and thereby it may be damaged when an over load occurs in the driving motor.